Table: table_user
userid (primary key)
no_changes_status (true means no update has been made on table_website for this userid)

Table: table_website
userid (reference key)
website_url (when the value of this field is changed, no_changes_status should be set to false)

DELIMITER $$

CREATE TRIGGER testref BEFORE INSERT ON table_website
  FOR EACH ROW BEGIN
    SELECT @aff_rows:=COUNT(*) FROM table_website WHERE yourCondition = sameConditionUsedForYourInsert
    AND (
    OLD.col1 != NEW.col1 OR
    OLD.col2 != NEW.col2 ...);
    IF @aff_rows > 0 THEN
       UPDATE table_user SET no_changes_status = whatever WHERE whatever;
    END IF;
  END;

$$
DELIMITER ;

SELECT ROW_COUNT();